🤖 Fix proofreading issues in bevy skills

- Fix `ref` keyword used as variable name in code examples
- Fix "retries next tick" → systems continue on normal schedule
- Fix `State::set()` → `NextState::set()` in upgrade skill
- Fix `SceneRoot` → `WorldAssetRoot` for 0.19 consistency
- Fix Replace lifecycle event description (overwritten, not removed)
- Fix grep patterns (quoting, trailing spaces)
- Remove third-party physics/networking content (not Bevy built-ins)

plugins/bevy/skills/bevy-0.19/SKILL.md

@@ -44,7 +44,7 @@ The highest-frequency mistakes. When in doubt, trust this table over memory:
 |------|--------|
 | Resources are components | Resources live on entities; `Query<Entity>` matches them — filter broad queries with `Without<IsResource>`. Cannot derive both `Component` and `Resource` on one type. |
 | Scene renamed | `Scene`/`SceneRoot` → `WorldAsset`/`WorldAssetRoot` |
-| `Ref<T>.clone()` | Returns `Ref<T>`, not the inner value — use `ref.deref().clone()` |
+| `Ref<T>.clone()` | Returns `Ref<T>`, not the inner value — use `my_ref.deref().clone()` |
 | `Assets::get_mut` | Returns `AssetMut<A>` (mutation-tracked), not `&mut A` |
 | GLTF materials | Return `GltfMaterial`; use `#Material0/std` label for `StandardMaterial` |
 
@@ -68,7 +68,7 @@ struct Player;
 
 ### Systems
 
-Plain functions of `SystemParam`s. Make fallible systems return `Result` (0.18+) — errors log and the system retries next tick; `?` works with anything convertible to `BevyError`:
+Plain functions of `SystemParam`s. Make fallible systems return `Result` (0.18+) — errors are logged via `BevyError` and the system continues running on its normal schedule; `?` works with anything convertible to `BevyError`:
 
 ```rust
 fn apply_damage(mut q: Query<&mut Health>, mut reader: MessageReader<Damage>) -> Result {
@@ -156,7 +156,7 @@ Bevy often succeeds silently when misconfigured. If something "doesn't show up"
 6. **Assets aren't ready after `load()`** — gate on `AssetEvent::LoadedWithDependencies` or `is_loaded_with_dependencies()`.
 7. **Raw `ButtonInput<MouseButton>` fires through UI** — world click handlers need UI-consumption checks.
 
-More production gotchas (physics, multiplayer/shared-world, custom relationships): `references/production-gotchas.md`.
+More production gotchas (custom relationships, debugging heuristics): `references/production-gotchas.md`.
 
 ## Code style
 
@@ -179,7 +179,7 @@ Load on demand — each is self-contained:
 | `references/events-observers.md` | Message vs Event APIs, observers, lifecycle events, hooks |
 | `references/input.md` | Keyboard, mouse, gamepad, touch |
 | `references/camera-rendering.md` | Cameras, coordinates, meshes, materials, shaders, assets, lighting |
-| `references/production-gotchas.md` | Silent failures, physics-plugin traps, headless/server architecture |
+| `references/production-gotchas.md` | Silent failures, headless contexts, debugging heuristics |
 
 ## Related skill